Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.34	3.749%	$57.4147	$57.41	$57.40	$57.40
Purchase #2	$200.88	12.246%	$225.4798	$225.48	$225.50	$225.50
Purchase #3	$153.82	6.169%	$163.3092	$163.31	$163.30	$163.30
Purchase #4	$123.32	13.853%	$140.4035	$140.40	$140.40	$140.40
Purchase #5	$213.61	5.584%	$225.538	$225.54	$225.55	$225.50
Purchase #6	$8.92	12.266%	$10.0141	$10.01	$10.00	$10.00
Purchase #7	$217.29	10.859%	$240.8855	$240.89	$240.90	$240.90
7 purchase totals =	$973.18		$1,063.0448	$1,063.04	$1,063.05	$1,063.00